The postal office in Norway tries hard to deliver to the correct destination. I've heard of similar stories where they only had a name and a city to go on, and it was delivered at the correct location. During Christmas, they even have a team of dedicated "detectives" who tries their hardest to figure out who the packages should be sent to.
Once, someone I knew in Norway (ok, my sister again...) somehow managed to combine her old and new address when ordering something online. And that parcel back and forth between 2 cities for a long time... :)
It's even better than that. Unless you are incredibly rural or the street is tiny, most streets have at least two postcodes - one for the odd side and one for the even side. In most cases, there's only about 15-30 houses in a postcode, any more on a road and it's split up into smaller chunks.